This prospective follow-up study addresses whether impulsivity versus other aspects of borderline personality disorder (BPD) are (1) stable over a 7-year follow-up period; (2) able to predict the persistence versus remittance of BPD over 7 years of follow-up, and (3) more predictive of the level of borderline psychopathology on follow-up than other aspects of the disorder. When the cohort was assembled, 88 of 130 subjects scored seven or higher on the Diagnostic Interview for Borderlines (DIB), indicating a definite diagnosis of BPD. The cohort was reassessed at 2 and 7 years after the index admission. At the 7-year follow up, 81(62.3%) of the original cohort were re-examined, two (1.6%) were deceased, six (4.6%) suicided, 36 (27.7%) refused to participate and five (3.8%) could not be located. The results indicated that the initial impulse action subscale score was highly correlated with the 7-year follow-up score (r = 0.53). Using a stepwise multiple regression technique, the impulse action subscale score from the DIB best predicted borderline psychopathology at the 7-year follow up, with an r2 of 0.24, F = 24.84, p < 0.001. This prospective study of subjects with BPD indicates that impulsivity is stable over time and highly predictive of borderline psychopathology over 7 years follow up. These results suggest the treatment of impulsivity may impact the course of BPD.